内蒙古车家营子地区晚侏罗-早白垩世侵入岩地球化学特征及地质意义

发布时间：2018-03-09 11:35

本文选题：车家营子地区　切入点：锆石U-Pb年代学　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文选择了广泛发育于内蒙古车家营子地区的晚侏罗-早白垩世侵入岩为研究对象,通过野外地质调查,对该地区晚侏罗-早白垩世侵入岩进行锆石U-Pb年代学、地球化学研究,确定了晚侏罗-早白垩世侵入岩的形成时代、岩石成因以及形成的构造环境。本文的研究结果不仅完善了车家营子地区的地质资料,同时还为大兴安岭中南部地区晚侏罗-早白垩世侵入岩的活动时间和构造演化历史提供了新的科学资料。本文讨论的车家营子地区晚侏罗-早白垩世侵入岩的岩性主要为细粒闪长岩、花岗闪长岩、黑云母花岗岩、二长斑岩、花岗闪长斑岩和花岗斑岩。其中最主要的花岗闪长岩LA-ICP-MS锆石U-Pb同位素年龄为138±10Ma,表明车家营子地区花岗闪长岩形成时代为早白垩世。车家营子地区晚侏罗-早白垩世侵入岩地球化学特征比较接近,具有富硅、富碱,贫钙镁的特征,样品w(SiO_2)为60.34%~77.43%,属于酸性岩类;w(Na_2O)/w(K_2O)为0.48%~1.5%,A/CNK为0.75~1.31之间,具有准铝质至过铝质系列岩石特点;哈克图解中,随着SiO_2含量增加,样品中Al_2O_3、Fe_2O_3、MgO、CaO、TiO_2、P_2O_5呈明显的负相关,K_2O呈明显正相关;样品稀土元素特点为轻稀土元素富集,重稀土元素亏损,具有不同程度的负Eu异常;富集Rb、Th等大离子亲石元素,亏损Ba、Nb、Ta等高场强元素;Rb与Th呈正相关变化;样品普遍含有角闪石,而不含白云母和石榴石等典型过铝矿物,均体现了I型花岗岩特点。通过地球化学特征以及构造判别显示车家营子地区晚侏罗-早白垩世花岗岩处于伸展-拉张构造环境,为地壳物质的部分熔融所形成,其形成可能与古太平洋俯冲有关。
[Abstract]:In this paper, the late Jurassic-early Cretaceous intrusive rocks widely developed in Chejiayingzi area, Inner Mongolia were selected as the research objects. Through field geological investigation, zircon U-Pb geochronology and geochemistry of the late Jurassic-early Cretaceous intrusive rocks in this area were studied. The formation age, genesis and tectonic environment of intrusive rocks in late Jurassic-early Cretaceous are determined. The results of this paper not only improve the geological data of Chejiayingzi area, but also determine the formation of the intrusive rocks in the late Jurassic-early Cretaceous. It also provides new scientific data for the activity time and tectonic evolution history of late Jurassic-early Cretaceous intrusive rocks in the central and southern part of Daxinganling Mountains. The late Jurassic-early Cretaceous intrusive rocks discussed in this paper. It is mainly fine-grained diorite. Granodiorite, biotite granite, monzomorphic porphyry, Granodiorite porphyry and granodiorite. The LA-ICP-MS zircon U-Pb isotopic age of the most important granodiorite is 138 卤10 Ma, indicating that the granodiorite was formed in the early Cretaceous in the Chejiayingzi area, and the late Jurassic-early Cretaceous age in the Chejiayingzi area. The geochemical characteristics of intrusive rocks are close to each other. It has the characteristics of rich in silicon, alkali and poor calcium and magnesium, the sample w _ (Sio _ 2) is 60.34 and 77.43, and belongs to the acidic rock class, Na2OO / wk _ (K _ 2O) is 0.481.5% ACNK = 0.75 ~ 1.31, and has the characteristics of quasi-aluminite to peraluminous series. In the Huck diagram, with the increase of SiO_2 content, There is a significant negative correlation between Al2O3FeSh and MgOTiO2TiO2P2O5 in the samples. The rare earth elements in the samples are characterized by the enrichment of light rare earth elements, the depletion of heavy rare earth elements, the negative EU anomalies, and the enrichment of large ion lithophile elements, such as RbTh. There was a positive correlation between RB and Th in the depleted high field strength elements, such as Ba, Nb, Ta, etc. The samples generally contained hornblende, but no typical peraluminous minerals such as Muscovite and garnet, etc. The geochemical characteristics and tectonic discrimination show that the late Jurassic-early Cretaceous granites are in extension-extensional tectonic environment and formed by the partial melting of crustal materials in the late Jurassic-early Cretaceous in the Chejiayingzi area. Its formation may be related to the subduction of the ancient Pacific Ocean.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.12

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